The Facilitatory Effects of Adjuvant Pharmaceutics to Prolong the Duration of Local Anesthetic for Peripheral Nerve Block: A Systematic Review and Network Meta-analysis

BACKGROUND: Peripheral nerve block (PNB) with perineural local anesthetic is used for anesthesia or analgesia with many benefits. To extend these benefits, various adjuvant drugs have been used to prolong the duration of analgesia. We aimed to evaluate the effectiveness of various adjuvants at prolonging the duration of sensory and motor blockade for PNB. METHODS: A network meta-analysis of placebo-controlled and active randomized controlled trials was performed comparing 10 adjuvants. Embase, PubMed, Web of Science, and Cochrane library were searched, with articles before May 21, 2020 included. Two authors independently selected studies and extracted data. The primary outcomes were sensory block (SB) and motor block (MB) time, and the secondary outcome was time of first analgesia rescue (FAR). Effect size measures were described as mean differences (MD) with 95% confidence intervals (CIs). Confidence in evidence was assessed using Confidence in Network Meta-Analysis (CINeMA). The study protocol was preregistered with the prospectively registered systematic reviews in health and social care international database (PROSPERO), as number CRD42020187866. RESULTS: Overall 16,364 citations were identified, of which 53 studies were included with data for 3649 patients. In network meta-analyses, 4 of 7 included treatment strategies were associated with more efficacious analgesia compared with placebo therapy, including dexamethasone (SB time: 5.73 hours, 95% CI, 4.16–7.30; MB time: 4.20 hours, 95% CI, 2.51–5.89; time of FAR: 8.71 hours, 95% CI, 6.63–10.79), dexmedetomidine (SB time: 4.51 hours, 95% CI, 3.52–5.50; MB time: 4.04 hours, 95% CI, 2.98–5.11; time of FAR: 5.25 hours, 95% CI, 4.08–6.43), fentanyl (SB time: 3.59 hours, 95% CI, 0.11–7.06; MB time: 4.42 hours, 95% CI, 0.78–8.06), and clonidine (SB time: 2.75 hours, 95% CI, 1.46–4.04; MB time: 2.93 hours, 95% CI, 1.69–4.16; time of FAR: 3.35 hours, 95% CI, 1.82–4.87). In a subgroup analysis, addition of dexamethasone to ropivacaine significantly increased the time of FAR when compared to dexmedetomidine (time of FAR: 5.23 hours, 95% CI, 2.92–7.54) or clonidine (time of FAR: 6.61 hours, 95% CI, 4.29–8.92) with ropivacaine. CONCLUSIONS: These findings provide evidence for the consideration of dexmedetomidine, dexamethasone, and clonidine as adjuvants to prolong the duration of PNB. The addition of dexamethasone to ropivacaine has a longer time of FAR compared with clonidine or dexmedetomidine.